Electrode for luminescent tubes



Jan. 9, 1934. R. R.y WILEY ET AL ELECTRODE FOR LUMINESCENT TUBES FiledMarch 5, 1929 mmmwmmmmwmwwmw Patented Jan. 9, 1934 ELECTRODE FORLU'IVIINESCENT TUBES Roya. Wiley and Alfred i.. Brandt, sr., Buffalo,

N. Y., assignors to Flexlume Corporation, Tonawanda, N. Y., acorporation of New York Application March 5, 1929. Serial No. 344,156 1claim. (cl. 17e- 126V 'I'his invention relates to improvements' in theelectrode construction of electroluminescent tubes and has particularreference to the protection of the lead-in wires of electrodes of thetype shown in a copending application serially numbered 320,150 whereinthe active electrode element is arranged within a body.

In electrode constructions of this type, the lead-in wire usuallyextends along vthe axial vcenter of rthe tube from thev exterior thereofthrough theglass seal of the reentrant stem to the body in which theactive element is located. According to the prior practice if the bodybe spaced from the glass seal, the intervening portion of the lead-inwire is ordinarily exposed to the surrounding gas. On the other hand, ifthe body be fused to the glass seal, the lead-in wirewill be insulatedfrom the surrounding gas. The fusion of the body to the glass seal is,however, ordinarily diflicult to accomplish, particularly when the bodyis composed of pyrex-glass which, as now considered, isl more desirablethan .other suitable substances. With the failure of the parts to fuseproperly, the lead-in wire obviouslyl remains exposed to the surroundinggas.

It has been observed that when any metal which is connected in thecircuit of the tube is placed in the axial center thereof, it will besubjected to an intensive electrical discharging action unless otherwiseprotected. Consequently it is necessary to protect theJead-in'wire whenexposed as above mentioned.

'I'he principal object of the invention is to provide a simpleconstruction which may be more or less roughly made and readilyassembled and which, nevertheless, will prevent-ahy discharge actionfrom centering around the lead-in wire.

An embodiment of the invention is illustrated.

in the accompanying drawing, wherein:

Figure 1 is a longitudinal section taken through the center of the tube.

Figure 2 is a section along line 2-2 of Figure 1.

Figure 3 is a longitudinal central section of a modified construction.

The electroluminescent tube is sufficiently indicated by a showing ofits terminal portionl in which the reentrant stern is provided with aglass seal 2 through which the lead-in wire 3.

passes. The electrode ,element 4 to which...the lead-in wire isconnected may be composed of any suitable material and fashioned in anysuitable form. Preferably it is composed of copper of foraminousstructure and arranged the form of a cylinder.

'Ille electrode element 4 is arranged within a chamber provided by a.body 5 of glass or other suitable insulating material which maybe of anysuitable form and supported in any suitable manner. As shown andpreferred, the body is made of cylindrical shape having the end throughwhich the lead-in wire passes closed as at 6. The electrode element ispreferably, although not necessarily anchored in the body.. This may beaccomplished by heating the body so as to cause it to flow into andflll'the foramina in the electrode, leaving a suitable area of thelatter exposed as an active area. The anchorage of the electrode elementin this manner considerably decreases vthe surface otherwise availableas an active area but even though this reduction of active surface becarried to an extreme the operation of the tube is not impaired;

The body is axially located within thetubepreferably with its closed endin abutting relation to the glass seal. The crevice existing betweenthese abutting parts is ordinarily sufficient to permit access of thegas with a resultant discharging action.

In order to prevent a discharging action from taking place and therebyprotect the lead-in wire,

a cylindrical sleeve l is utilized. This. sleeve conforms roughly to andfits somewhat closely over the body and also conforms roughly to, and tssomewhat closely over the re'entrant stem 85 of thevtube. One end of thesleeve bears against the end of the tube and the opposite end of -thesleeve 7 indicated at 7b isl cup-shaped, that is to say flared outwardlyinto contact with the walls' of the tube and extended forwardlyalong 90the walls thereof. Thus both the stem andthe body are telescoped Withinand in substantial contact with the sleeve 7. Y

With this arrangement it .is evident that two gas paths extend from theexposed lead-in wire to the tube proper, one between the sleeve. and thebody and the other around the outer surface of the sleeve. While thesleeve is intended to fit` accurately on the body and the other partsmentioned, the difficulty of obtaining accurate di- 100 mensions inglass Work of this type renders this practically impossible. Thevariations in the dimensions will, therefore, insure the existence ofthe gas paths mentioned. However, the areas of such paths are greatlyrestricted for a considerable portion of ltheir length and consequentlythe resistance of the paths to the current flow is very high. Wehavefound that when the sleeve is roughly made the variations naturallyoccurring are not suicient to reduce the resistance to the current ofeither or both paths to an extent such as will permit a dischargingaction.

The diameter of that portion of the sleeve which extends between the end7b and the body is preferably reduced to provide a restricted convnecting passage 8 between the electrode and the tube proper. The passage8 functions to reduce the rate of vaporization of the electrode aspointed out in the copending application noted.

In the modied form of construction shown, in Figure 3, the body isslightly spaced from the reentrant stem while the connecting passage isformed directly on the body instead of on the sleeve '7, the details ofconstruction being the same otherwise. This form of construction as wellas the form shown in Figures 1 and 2, has the advantage of facilitatingthe manufacture of the tube. During such manufacture, after the body hasbeen properly arranged, the electrode`construction is completed simplyby slipping the esv and extending through a wall of said body, and

a -sleev.e tting over said body and having a cupshaped end extendingforwardly of said body in contact with the walls of said tube, theportion of said sleeve extending between said body and said cup-shapedend being of reduced diameter to provide ya restricted passageconnecting the interior of the body to the tube proper. ROY'R. WILEY. I

ALFRED L. BRANDT, Sn.

